Forward looking infrared (FLIR) sensors are imaging devices that detect infrared radiation to create an image of a scene. FLIR sensors commonly utilize a two dimensional array of pixels such as a focal plane array (FPA) to form the infrared image. The pixels of infrared FPAs, for example, are formed of a material that is sensitive to infrared radiation, such as indium antimonide (InSb), Mercury Cadium Telluride (MCT), or other infrared-sensitive materials. FLIR sensors are typically configured to operate within long-wave infrared (e.g., 8-14 μm) and mid-wave infrared (e.g., 3-5 μm) bands. Infrared light is focused onto the pixels of the FPA which then generate a signal such as a voltage that corresponds to the level of infrared light detected. The signals generated by the pixels may then be sent to other internal or external system electronics to be compiled into a thermal image of the scene. As many infrared FPAs operate most effectively at very cold temperatures, the FPAs of FLIR sensors are commonly cryogenically cooled within a dewar flask.
Particular FLIR sensors may be configured to filter infrared radiation to a particular channel. For example, a FLIR sensor may incorporate a filter that provides either multi-spectral (i.e., Red, Green and Blue regions of a nominal wavelength band under detection), polarimetric or panchromatic filtering. Multi-spectral and polarimetric imagery utilize the comparison of the images from each channel, and therefore require accurate image registration to prevent false signals. Therefore, simultaneous capture of multi-spectral and polarimetric imagery is required. Under current FLIR design, a single FLIR sensor is either dedicated to one particular channel by a single passband filter, or is filtered at the individual pixel level, which requires very small filter patterns at the pixel pitch dimension. Such small filters or small filter patterns are difficult and expensive to manufacture and implement in a FLIR sensor. Additionally, requiring at least one FLIR sensor for imaging in each desired channel adds significant weight to the imaging system, should simultaneous capture of multi-spectral and polarimetric imagery be desired.
FLIR sensors or cameras are utilized in many applications, including target acquisition in naval vessels and aircraft, surveillance, search and rescue, and use on unmanned aerial vehicles (UAVs). Particularly, FLIR sensors require technology for high-resolution imagery with contrast enhancement for better target identification. Further, some applications, such as those aboard an UAV, which are commonly extremely light and cannot carry significant weight, require FLIR sensors that provide for high-resolution imagery and low noise attributes in a package of very low mass and volume. Therefore, high-resolution imagery in such applications should be achieved with the use of minimal, lightweight components.